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Substitution troubles
by Jeremy Jay 25 Feb '09

25 Feb '09

Hello all, I'm new to GiNaC, but so far I've been very impressed by its power. But, I seem to be having a problem with the substitutions, can anyone tell me what I'm doing wrong? A short example is the following code: ---- #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; ////////////////////////////////////////////////////////////// // delta( c_i, c_j ) = 1 if c_i==c_j otherwise 0 DECLARE_FUNCTION_2P(delta); REGISTER_FUNCTION(delta, dummy()); ////////////////////////////////////////////////////////////// int main(int argc, char **argv) { symbol q("q"), c0("c0"), c1("c1"), c2("c2"); ex poly( (1-delta(c0,c1))*(1-delta(c0,c2)) ); poly=poly.expand(); cout << "START : " << poly << endl; poly = poly.subs( 1 == q ); cout << "sub 1 => q : " << poly << endl; return 0; } ---- which gives the output: ---- START : 1-delta(c0,c2)-delta(c0,c1)+delta(c0,c2)*delta(c0,c1) sub 1 => q : 1-delta(c0,c2)-delta(c0,c1)+delta(c0,c2)*delta(c0,c1) ---- which is not what I would expect. I've also tried using the 'numeric' type instead of the literal 1's, but get the same effect. Am I missing something? BTW, for anyone interesed in the point of this, I'm trying to implement the algorithm in this paper: http://www.iop.org/EJ/abstract/1367-2630/11/2/023001/ Thanks in advance! Jeremy

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Polynomial companion matrix
by James Jackson 18 Feb '09

18 Feb '09

Hi, As far as I can see, there is no method available to compute the companion matrix of a polynomial. May I suggest the addition of a method along these lines?: // Creates the Companion matrix for a given polynomial GiNaC::matrix CreateCompanion(const GiNaC::ex &poly, const GiNaC::ex &symbol) { if(poly.is_polynomial(symbol)) { int rank = poly.degree(symbol); GiNaC::matrix mat(rank, rank); GiNaC::ex majorCoeff = poly.coeff(symbol, rank); for(int i = 0; i < rank; ++i) { for(int j = 0; j < rank; ++j) { if(i - j == 1) { mat(i, j) = 1; } else if(i == 0) { mat(i, j) = -1 * poly.coeff(symbol, rank - j - 1) / majorCoeff; } } } return mat; } else { // Throw exception or return empty matrix } } Regards, James.

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Release GiNaC 1.5.0
by Jens Vollinga 17 Feb '09

17 Feb '09

Hi everybody, GiNaC 1.5.0 is out and available. The changes are: * Added polynomial factorization. * New, faster (recursive descent) expression parser. * Faster GCD computation. * gcd() now allows the user to override (some of the) heuristics. * Writing extensions classes is simpler now: - Replaced custom RTTI by standard C++ RTTI. - Definition of archiving methods now optional when declaring a new GiNaC class. * Fixed recursion in polynomial divide that caused a significant slowdown in sqrfree(). * Improved lsolve() of systems containing non-numeric coefficients. * Removed implicit conversions from cl_N to numeric. * Improved configuration and compatibility. This is a new branch that introduces some incompatibilities on the source code level! If you have defined your own GiNaC classes, you will have to change their definitions slightly (cf. section 6.5.6 in http://www.ginac.de/tutorial/Adding-classes.html#Adding-classes) As always, this release can be downloaded from http://www.ginac.de/Download.html Best wishes, Jens

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Calculating Matrix eigenvalues?
by James Jackson 17 Feb '09

17 Feb '09

Hi, I'm wondering if the Matrix class permits the calculation of eigenvectors / values? I'm guessing, reading the docs, that this isn't implemented, but thought I'd check! Regards, James.

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Not factoring expression
by James Jackson 17 Feb '09

17 Feb '09

Hi, I've just started using GiNaC (and very nice it is too!), however I have some strange behavior with an expression not being simplified. One output of a linear equation solver is the expression: (C_2 *s ^ 2 *L_2 *V_1 + C_2 *L_1 *C_1 *s ^ 4 *L_2 *V_1 + L_1 *C_1 *s ^ 2 *V_1 + V_1 )*(1 +L_1*C_1*s^2+C_2*L_1*s^2+C_2*L_1*C_1*s^4*L_2+C_2*s^2*L_2)^(-1)*V_1^(-1) What is happening is that the V_1 terms in the first bracket are not being factorised, and therefore no cancellation with the final (V_1)^(-1) term is occuring. All my symbols are created with a SymbolFactory pattern, so I can be sure each V_1 is the same object. Can anyone suggest why GiNaC isn't simplifying this to cancel the V_1 terms? Regards, James.

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symbolic matrix
by Luis Rivera 19 Jan '09

19 Jan '09

Hello Vladimir, Thanks a lot. Regards Luis Créez votre adresse électronique prenom.nom(a)laposte.net 1 Go d'espace de stockage, anti-spam et anti-virus intégrés.

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symbolic matrix
by Luis Rivera 19 Jan '09

19 Jan '09

Hello Vladimir, Thanks for your answer. Yes, if I use the code below it works. Could you explain me in few words why it should be so? Thanks, Luis New version: ########### ex A; A = symbolic_matrix(n,n, "A"); cout << "A(0,0) = " << ex_to<matrix>(A)(0,0) << endl; cout << "A(0,1) = " << ex_to<matrix>(A)(0,1) << endl; cout << "A(1,0) = " << ex_to<matrix>(A)(1,0) << endl; cout << "A(1,1) = " << ex_to<matrix>(A)(1,1) << endl; ########### ------------------------------------------------------------------------------------ >>>>> On Mon, 19 Jan 2009 21:07:58 +0100 (CET), Luis Rivera <luis.rivera(a)laposte.net> >>said: >> LR> I have some problem accessing the elements of a symbolic matrix. >> LR> For example the code below creates a 2x2 symbolic matrix 'A' but >> LR> I can't access the individual elements. >> > A similar question was asked here recently: > > http://www.ginac.de/pipermail/ginac-list/2008-November/001458.html > > see if its answer would work for you. > > Best wishes, > Vladimir Créez votre adresse électronique prenom.nom(a)laposte.net 1 Go d'espace de stockage, anti-spam et anti-virus intégrés.

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symbolic matrix
by Luis Rivera 19 Jan '09

19 Jan '09

Hello, I have some problem accessing the elements of a symbolic matrix. For example the code below creates a 2x2 symbolic matrix 'A' but I can't access the individual elements. The output I get when I run the small program below is: [luis@urubamba ~/GiNaC]#87 ./AA A(0,0) = [[A00,A01],[A10,A11]] matrix::operator(): index out of range What am I making wrong? Thanks for any hint. Luis #############################33 #include <iostream> #include <stdexcept> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main() { int j,k,n=2; try{ matrix A; A = symbolic_matrix(n,n, "A"); cout << "A(0,0) = " << A(0,0) << endl; cout << "A(0,1) = " << A(0,1) << endl; cout << "A(1,0) = " << A(1,0) << endl; cout << "A(1,1) = " << A(1,1) << endl; } catch (exception &z) { cerr << z.what() << endl; return 1; } return 0; } ######################### Créez votre adresse électronique prenom.nom(a)laposte.net 1 Go d'espace de stockage, anti-spam et anti-virus intégrés.

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Re: [GiNaC-list] GiNaC-list Digest, Vol 47, Issue 2
by Luca Dall'Olio 15 Jan '09

15 Jan '09

ginac-list-request(a)ginac.de ha scritto: > Send GiNaC-list mailing list submissions to > ginac-list(a)ginac.de > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.cebix.net/mailman/listinfo/ginac-list > or, via email, send a message with subject or body 'help' to > ginac-list-request(a)ginac.de > > You can reach the person managing the list at > ginac-list-owner(a)ginac.de > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of GiNaC-list digest..." > > > Today's Topics: > > 1. Re: constrained, parametric optimization (Richard B. Kreckel) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 14 Jan 2009 10:29:40 +0100 > From: "Richard B. Kreckel" <kreckel(a)ginac.de> > Subject: Re: [GiNaC-list] constrained, parametric optimization > To: GiNaC discussion list <ginac-list(a)ginac.de> > Message-ID: <496DB084.2060308(a)ginac.de> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Luca Dall'Olio wrote: > >> I am developing a computer program which needs to solve a constrained, >> parametric optimisation, something like : >> >> meaning to calculate min(x) such as y = b*x+a and x <= c and x >=0 >> where x and y are variables, a, b, c are constant but unknown parameters. >> Since the problem is calculated at runtime from my computer program and >> changes every time, I think I need to solve it with some form of constrained >> programming with a symbolic result. >> >> I could see something like this in mathematica : >> >> http://reference.wolfram.com/mathematica/ref/Minimize.html#61381153 >> >> but I would like to keep my program free and open source, so I would like to >> use a free library for this... >> >> could you please tell me if I can do this using ginac? >> > > GiNaC isn't prepared to do constrained optimization. > thank you very much for saving me a lot of (unsuccessful) time searching :-) > I suppose that the example you posted above isn't the most general case > you are aiming at. > yes, you are right > > Because if it is, you can of course do that manually. > However, if the equations start containing powers of x, things become > more nasty. > I agree, I could live with limitations such as "only linear objective function, only inequality constraints ..." or things like that, but I need a parametric input (and so a symbolic result) > Regards > -richy. > Best regards, Luca

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constrained, parametric optimization
by Luca Dall'Olio 14 Jan '09

14 Jan '09

I am developing a computer program which needs to solve a constrained, parametric optimisation, something like : meaning to calculate min(x) such as y = b*x+a and x <= c and x >=0 where x and y are variables, a, b, c are constant but unknown parameters. Since the problem is calculated at runtime from my computer program and changes every time, I think I need to solve it with some form of constrained programming with a symbolic result. I could see something like this in mathematica : http://reference.wolfram.com/mathematica/ref/Minimize.html#61381153 but I would like to keep my program free and open source, so I would like to use a free library for this... could you please tell me if I can do this using ginac? thank you very much in advance! Luca

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